Electromechanical clock

ABSTRACT

A timepiece with an electrodynamically controlled clockwork has a torsion ndulum intermittently coupled through a gear train with the clockwork for the maintenance of its oscillations. The gear train includes a first pinion mounted on a weighted rocker tending to hold it in mesh with a driving gear actuated by the clockwork; the torsion spring of the pendulum carries near its suspension point a horizontal spur receivable in a slot of a stationary mounting member so as to come periodically to rest on a slot edge, this spur being engageable in its arrested position by a hump on a cam disk entrained by a second pinion which meshes with the first pinion and decouples the latter from the associated gear against the countervailing force of the rocker weight as long as the spur is immobilized. When the spur-biasing force of the torsion spring changes direction, the gear train is re-established and the spur receives an impetus from the engaging hump as it moves away from the arresting slot edge.

This application is a reissue of U.S. Pat. No. 3,990,226. .Iaddend.

FIELD OF THE INVENTION

The present invention relates to a timepiece provided with anelectrodynamically controlled clockwork and a torsion pendulum.

BACKGROUND OF THE INVENTION

Torsion pendulums, which have oscillatory cycles on the order of tens ofseconds, have been used in the art of chronometry for a long time. Thelarge time constants of these torsion pendulums minimize their energyconsumption so that spring-loaded clocks of this type can be operatedfor a long period without rewinding. In electrically powered clockworkstheir current consumption is minimal.

This low energy consumption, on the other hand, makes such a clockworksensitive to impact .[.timepiece;.]. .Iadd.or .Iaddend.vibration andalso requires a level base for the .[.timpiece.]..Iadd.timepiece.Iaddend.; thus, clocks of this type are liable tooperate irregularly or to stop prematurely. Even with precisionmanufacture, they are difficult to calibrate properly in order to keeptime with a reasonable degree of accuracy.

Nevertheless, timepieces with torsion pendulums have found wide publicacceptance presumably due to the esthetic appeal and nerve-soothingeffect of a pendulum weight oscillating with a slow rhythm about avertical axis. The pendulum weight itself is usually of ornamentaldesign, frequently comprising a pair of intersecting arms carrying metalballs at their ends.

Thus, it has already been proposed to equip a timepiece with a normalclockwork and a torsion pendulum. If the pendulum is provided with itsown stepping mechanism independent of the functional clockwork, such asa Graham escapement, the timpeiece becomes complex and correspondinglyexpensive. Earlier suggestions for an operative coupling between theclockwork and the torsion pendulum, however, entail various drawbacks.According to German published specifications Nos. 1,798,274 and1,936,654, for example, the clockwork is controlled by an escapement ofthe sling-drive type whose oscillating weight acts upon the torsionspring of the pendulum through a coupling between that spring and thesling mounting. The interaction between two systems of different naturalfrequencies generates interference phenomena which may arrest thependulum and also can adversely affect the operation of the clockworkitself, in the absence of special synchronization circuits as disclosedin the second one of these publications. A contactless magnetic couplingbetween the clockwork and the torsion pendulum, as described in Germanpublished specification No. 2,058,037, avoids some of these difficultiesbut requires a strong magnetic field in its practical realization, witha correspondingly bulky structure. Moreover, such magnetic couplings arenot practical with electrodynamically driven clockworks which aresusceptible of malfunction caused by stray magnetic flux and whichtherefore require high-precision workmanship.

OBJECTS OF THE INVENTION

The general object of this invention, therefore, is to provide acompact, simple and reliable timepiece of the character referred towhich avoids the aforestated disadvantages.

A more particular object is to provide a clockwork with a stepping drivefor a torsion pendulum which can be operated by an electrodynamicescapement realizable with integrated circuitry.

SUMMARY OF THE INVENTION

These objects are realized, pursuant to the present invention, by theprovision of a mechanical transmission between a clockwork, powered by asource of electric energy, and the resilient element of a torsionpendulum whereby the latter can be periodically stepped, thetransmission including decoupling means controlled by the flexibleelement for interrupting the power train therethrough during apredetermined phase of each oscillatory cycle of the pendulum for thepurpose of periodic resynchronization.

Pursuant to a more particular feature of the invention, the mechanicaltransmission comprises a gear train including a driving gear, preferablyon a relatively fast-moving shaft such as the one advancing the secondhand of the timepiece, and two permanently meshing pinions, the first ofthese pinions being entrainable by the driving gear but beingdisengageable thereform by being journaled in movable mounting meanssuch as a rocker pivoted to a stationary support for swinging about ahorizontal axis. The position and sense of rotation of the two pinionsare such that the first pinion, when entrained, tends to displace theengaged teeth of the second pinion toward the axis of the driving gearwith resulting disengagement of the first pinion from that gear wheneverthe second pinion is halted. The rocker carrying the first pinion isbiased, e.g. by gravity, in a sense tending to maintain that pinion inmesh with the driving gear; the swing of the rocker may be limited by acutout in the fixed support receiving the shaft of the first pinion. Theresilient element or torsion spring of the pendulum is formed with anextension, advantageously a horizontal spur secured to it (e.g. bymolding) near its fixedly anchored upper end, which oscillates with thatspring and .[.in.]. .Iadd.is .Iaddend.intermittently engageable by aformation on a driven member positively coupled with the second pinion.Once during each pendulum cycle the spur engages a fixed stop, e.g. anedge of a horizontal slot in the rocker support, so as to be immobilizedfor a time interval preferably approximating half an oscillatory period;during this standstill period the coacting formation of the drivenmember--specifically a hump of a cam disk--comes into contact with thespur whereby the second pinion is arrested and the first pinion isretracted from the driving gear until the spur is released on the returnswing of the pendulum.

The rocker, the pinions and the cam disk advantageously consist ofplastic material in order to be of light weight and have a low moment ofinertia.

BRIEF DESCRIPTION OF THE DRAWING

The above and other features of the invention will now be described indetail with reference to the accompanying drawing in which:

FIG. 1 is a rear elevational view of a clockwork and stepping drive of atimepiece equipped with a torsion pendulum according to the invention;

FIG. 2 is a top view of the assembly of FIG. 1;

FIGS. 3 and 4 are side-elevational views as seen in the directions ofarrows III and IV, respectively, in FIG. 1;

FIG. 5a is an enlarged rear view of some of the components seen in FIG.1;

FIG. 5b is a top view of the components of FIG. 5a, drawn to the samescale;

FIG. 5c is a detail view as seen on the line Vc--Vc in FIG. 5b; and

FIG. 6 is a circuit diagram of an electrodynamic escapement for theclockwork of FIG. 1.

SPECIFIC DESCRIPTION

In FIGS. 1-5c there is shown an upright supporting plate 60 rigid with anonillustrated clock housing. Plate 60 carries stepped rods 61 whichpass through an intermediate plate 62 and a back plate 14 spaced apartby sleeves 63 and held in position by screws 64. A balance wheel 20 hasa shaft 20' journaled between bearing screws 21 (only one shown)threaded into a lower lug 65 and a nonillustrated upper lug bothprojecting rearwardly from plate 60. Balance wheel 20 comprises theusual spiral spring 22 which is fastened by a screw 24 to a lug 23 alsocarried on the rear face of plate 60. The other end of spring 22 isanchored to a lever 25 which is fulcrumed on screw 21 and whose oppositeend 25' engages in the threads of an adjusting bolt 26 screwed intoplate 60. Balance wheel 20 comprises a pair of parallel horizontal disks28 carrying two oppositely polarized permanent magnets 27 as well as apair of diametrically opposite counterpoises 29. The electrodynamicactuation of balance wheel 20 with the aid of magnets 29 will bedescribed hereinafter with reference to FIG. 6.

Balance wheel 20 is part of a clockwork which also includes steppingmeans 40 for the advance of the clock hands (not shown), comprising aresilient pawl 41 which is mounted on a head 42 of shaft 20' and coactswith a ratchet 43 for clockwise rotation as viewed in FIG. 5a. Ratchet43 is rigid with a pinion 44 which is journaled in back plate 14 andmeshes with a gear 5 driving the second hand (not shown) of the clock.Ratchet 43 is periodically arrested by a nonillustrated retaining pawlin the well-known manner.

Gear 5, keyed to the drive shaft 5' for the second hand (not shown), isrigid with a pinion 51 driving a gear 52 whose shaft 53 is journaled inplates 14 and 60. Gear 52, preferably made of plastic material, drivesvia a pinion 54 a gear 55 which is coupled through a friction clutch 56with a central shaft 57 carrying the nonillustrated minute hand, thisshaft being journaled in plates 60 and 62. A pinion 58, rigid with gear55, engages a reversing gear 59 whose shaft 70 is also journaled inplates 60 and 62; the forward end of shaft 70 extends into anonillustrated front recess of plate 60 where it meshes with anotherreversing gear, not shown, to drive a tubular shaft 71 for the hour handcoaxial with minute shaft 57.

A post 31, integral with one of the mounting rods 61, carries amicroelectronic module 30 which comprises a printed base plate 32,capacitors 33 and 34, a resistor 35 and an integrated-circuit chip 36. Acontact spring 38, serving to complete certain internal connections ofmodule 30, is engaged by a screw 39 which passes through the base plate32 and secures it to the post 31. Plate 32 supports an electromagneticyoke 37 projecting into the path of magnets 29. Further details of thiscircuitry will be described below with reference to FIG. 6. Current issupplied to the module 30 via a nonillustrated lead connected to theforwardly projecting end of the metallic mounting screw 39 which, ofcourse, is well insulated with reference to grounded metallic parts ofthe system; the other supply terminal is constituted by the groundedclock housing.

In accordance with the present invention, a torsion pendulum 9 issuspended on a resilient elongate element 3 (referred to hereinafter asa torsion spring) whose upper end is clamped in a fixed spring mounting19. This torsion pendulum is linked with the clockwork 20, 40 via a geartrain, generally designated 50, which comprises a pair of pinions 6, 7as well as the secondhand gear 5. Pinion 6 is mounted on a shaft 17which is journaled in a rocker 12 having a free end loaded down by aweight 12', the shaft 17 projecting into a cutout 18 of plate 14. Theupper and lower edges 13' and 13" of this cutout limit the swing of therocker about a horizontal axis 10 defined by a shaft 11 journaled inplates 14 and 60, rocker 12 having a hub 16 surrounding this shaft. Acam disk 1 carried on shaft 11 has two diametrically opposite humps 2positioned to coact with an end 4' of a spur 4 which, as best seen inFIG. 5c, is rigid with torsion spring 3; this spur advantageouslyconsists of a resinous casting directly molded on the spring 3 at alocation a small fraction of its length below mount 19. The end 4' ofspur 4 is receivable in a horizontal slot 14' of plate 14 where it comesto rest against a stop 8 formed by an edge of that slot substantially inline with shaft 11; it is only in the vicinity of this edge that thehumps 2 may contact the spur 4. Thus, torsion spring 3 biases the spur 4against the stop 8 during part of a pendulum cycle, with a forceeffective in a clockwise sense as viewed in FIG. 5b; during theremainder of the cycle that force is reversed and disengages the spurfrom the stop.

Pinion 6 is stepped and has two toothed portions 6' and 6" of larger andsmaller diameter, respectively. Toothed portion 6' permanently mesheswith pinion 7; toothed portion 6" is urged by the weight 12' intoengagement with driving gear 5 by which it is set in clockwise rotationas viewed in FIG. 5a. With pinion 7 rotating counterclockwise, thecontacting teeth of pinions 6 and 7 move toward the axis of gear 5whereby pinion 7 exerts upon pinion 6 a reaction force tending todisengage it from gear 5. This reaction force is negligible as long aspinon 7 is free to rotate about its axis 10; when that rotation isstopped, however, by contact between a hump 2 of disk 1 and the spur 4arrested by stop 8 as described hereinafter, pinion 6 rides up theperiphery of pinion 7 under the driving force of gear 5, against thecountervailing effect of weight 12', until its portion 6" no longerengages the teeth of gear 5. With elements 1, 5, 6, 7 and 12 made oflight-weight plastic material, this disengagement proceeds with littlefriction and without generation of objectionable noise.

The electrodynamic escapement drive for the clockwork 20, 40 has beenshown in FIG. 6. Chip 36 comprises two NPN transistors T₁, T₂, a diodeD, and a voltage divider formed by a pair of resistors R₁, R₂. Yoke 37is shown to comprise a pair of coils L₁, L₂ connected in series withcapacitor 33 and resistor 35 between a positive bus bar B+ and ground;resistor 35 is shunted by capacitor 34. Transistor T₁, whose collectoris tied to bus bar B+, has its base connected to the junction ofimpedances 33-35 and, via diode D, to the collector of transistor T₂whose emitter is grounded. The emitter of transistor T₁ is connected onthe one hand to the junction of coils L₁, L₂ and on the other hand toground via resistors R₁ and R₂ whose common terminal is tied to the baseof transistor T₂.

When power is first connected to the system, capacitor 33 chargesthrough resistor 35 and turns on the transistor T₁ to energize the coilL₂ along with the coil L₁ which is inductively coupled therewith. Thesimultaneous flow of charging current into capacitor 33, which islimited by the conductive condition of transistor T₂, is reversed uponthe return swing of the magnets with resulting cutoff of bothtransistors. Capacitor 34 then charges until the magnetically inducedreverse voltage disappears whereupon transistor T₁ conducts again andre-energizes the coils 37. The cycle is then repeated.

The foregoing explanation is given merely by way of example and is notmaterial to the operation of the stepping mechanism for the torsionpendulum 9 which will now be described.

It will be assumed that torsion pendulum 9 has a neutral position inwhich the spur 4 just contacts the edge 8 of slot 14'. During thequarter-cycle in which the pendulum rotates in one direction (i.e.counterclockwise as viewed in FIG. 5b), from that neutral position, andduring the subsequent return swing to that neutral position, thisrotation is not impeded by the stop 8 and the natural frequency of thependulum is determined by the full length of torsion spring 3; thehalf-cycle consisting of these two quarter-turns is therefore ofslightly larger duration t' than the other half-cycle in which the spur4 is stopped so that the slight foreshortening of spring 3 results in ahigher natural frequency, corresponding to a shorter duration t". Thetotal oscillatory period is thus t'+t".

The transmission ratio between gear 5 and pinion 7 is so chosen that camdisk 1 performs half a revolution in a time greater than t' but lessthan t" so that one of its humps 2 will always engage the spur 4 restingagainst stop 8. Until the pendulum swings again through its neutralposition, cam disk 1 is immobilized and therefore disconnects the pinion6 from driving gear 5. Thus, the clockwork 20, 40 and the stepping drive50 for the pendulum 9 are resynchronized at a precise point in eachoscillatory cycle, this resynchronization being accompanied by a briefacceleration of spur 4 at the beginning of its counterclockwise swing(FIG. 5b) by an impetus from the engaging hump 2 which rolls on its end4' and eventually becomes disengaged therefrom.

In principle, the neutral point of the pendulum oscillation could be sochosen that the spur 4 remains immobilized by the edge 8 for a longer orshorter fraction of a cycle. The arresting of this spur in mid-cycle,however, has the advantage of a smooth and virtually unnoticeablechangeover between the two oscillating frequencies of the pendulum.

In a particularly advantageous embodiment, with a torsion pendulumperforming a full oscillation in about 10 to 15 seconds, the elements ofthe gear train associated with the two-hump cam disk 1 were constructedas follows:

    ______________________________________    driving gear 5           72 teeth    small-diameter portion 6' of pinion 6                             22 teeth    large-diameter portion 6" of pinion 6                             20 teeth    pinion 7                 20 teeth    ______________________________________

Since on standstill the spur 4 lies next to the stop 8 in a positionfrom which it can be dislodged by a hump 2 upon incipient rotation ofcam disk 1, no manual startup of the pendulum 9 is necessary when theclockwork is set in motion. The same clockwork can be used to drive twoor more torsion pendulums, of mutually different natural frequencies, aslong as the aforestated relationship between transmission ratio andoscillatory period is preserved.

I claim: .[.
 1. In a timepiece, in combination:a clockwork powered by asource of electric energy; a nonfunctional torsion pendulum with anelongate resilient element having a fixedly anchored upper end and afreely rotatable weighted lower end; mechanical transmission meansbetween said clockwork and said resilient element for periodicallystepping said torsion pendulum; and decoupling means in saidtransmission means controlled by said resilient element for interruptingthe power train therethrough during a predetermined phase of eachoscillatory cycle of said torsion pendulum..].
 2. .[.The combinationdefined in claim 1 wherein said.]..Iadd.In a timepiece, in combination:aclockwork powered by a source of electric energy; a torsion pendulumwith an elongate resilient element having a fixedly anchored upper endand a freely rotatable lower end; mechanical .Iaddend.transmission means.[.comprises.]. .Iadd.comprising .Iaddend.a gear train including adriving gear positively coupled with said clockwork, a first pinionpositioned adjacent said driving gear for entrainment thereby, movablemounting means for said first pinion enabling its disengagement fromsaid driving gear, a second pinion meshing with said first pinion with asense of rotation tending to disengage said first pinion from saiddriving gear upon a halting of said second pinion, biasing means forsaid mounting means tending to maintain said first pinion engaged withsaid driving gear, and a driven member positively coupled with saidsecond pinion; .[.said.]. .Iadd.and .Iaddend. decoupling meanscomprising an oscillatable extension of said resilient element, aformation on said driven member intermittently engageable with saidextension, and stop means periodically engageable by said extension in.[.said.]. .Iadd.a predetermined .Iaddend.phase of an oscillatory cycle,said extension lying in the path of said formation only in the vicinityof said stop means and resisting displacement by said formation whilebeing urged by said resilient element against said stop means.Iadd.,said mounting means comprising a rocker pivoted to a stationary supportfor swinging about a horizontal axis, said stop means being part of saidsupport. .Iaddend. .[.3. The combination defined in claim 2 wherein saidmounting means comprises a rocker pivoted to a stationary support forswinging about a horizontal axis, said stop means being part of saidsupport..].
 4. The combination defined in claim .[.3.]. .Iadd.2.Iaddend.wherein said extension comprises a horizontal spur secured tosaid resilient element near said upper end thereof for oscillationthereabout.
 5. The combination defined in claim 4 wherein said stopmeans is an edge of a horizontal slot in said support periodicallyenterable by said spur.
 6. The combination defined in claim 4 whereinsaid driven member is a cam disk, said formation being at least one humpon said cam disk.
 7. The combination defined in claim 6 wherein saidstop means substantially coincides with a vertical axial plane of saidcam disk.
 8. The combination defined in claim 7 wherein said horizontalaxis lies in said vertical plane, said rocker being provided with apivot pin carrying said cam disk.
 9. The combination defined in claim 8wherein said biasing means comprises a weight at an extremity of saidrocker remote from said pivot pin, said first pinion being carried onsaid rocker at an intermediate location between said extremity and saidaxis.
 10. The combination defined in claim 8 wherein said second pinionis mounted on said pivot pin and is rigid with said cam disk.
 11. Thecombination defined in claim 10 wherein said first pinion is stepped andhas two toothed portions of different diameter respectively meshing withsaid driving gear and with said second pinion.
 12. The combinationdefined in claim 11 wherein the toothed portion meshing with said secondpinion has the larger diameter.
 13. The combination defined in claim 12wherein said driving gear is substantially larger than said pinions. 14.The combination defined in claim 13 wherein said driving gear has 72teeth, said toothed portions have 22 and 20 teeth, respectively, andsaid second pinion has 20 teeth.
 15. The combination defined in claim 14wherein said cam disk is provided with two diametrically opposite humpsand said torsion pendulum has an oscillatory cycle of about 10 to 15seconds.
 16. The combination defined in claim 8 wherein said support isprovided with a cutout, said first pinion being provided with a shaftreceived with play in said cutout for limiting the swing of said rocker.17. The combination defined in claim 6 wherein said pinions, said rockerand said cam disk .[.consists.]. .Iadd.consist .Iaddend.of plasticmaterial.
 18. The combination defined in claim 4 wherein said spur is aresinous casting on said resilient element.
 19. The combination definedin claim 2 wherein said extension engages said stop means substantiallyin a midposition of a pendulum swing. .[.20. The combination defined inclaim 1 wherein said clockwork comprises an electrodynamicescapement..]. .Iadd. In a timepiece, in combination:a clockwork poweredby a source of electric energy; a torsion pendulum with an elongateresilient element having a fixedly anchored upper end and a freelyrotatable lower end; mechanical transmission means comprising a geartrain including a driving gear positively coupled with said clockwork, afirst pinion adjacent said driving gear for entrainment thereby, movablemounting means for said first pinion enabling its disengagement fromsaid driving gear, a second pinion meshing with said first pinion with asense of rotation tending to disengage said first pinion from saiddriving gear upon a halting of said second pinion, biasing means forsaid mounting means tending to maintain said first pinion engaged withsaid driving gear, and a driven member positively coupled with saidsecond pinion; and decoupling means comprising an oscillatable extensionof said resilient element, a formation on said driven memberintermittently engageable with said extension, and stop meansperiodically engageable by said extension in a predetermined phase of anoscillatory cycle, said extension lying in the path of said formationonly in the vicinity of said stop means and resisting displacement bysaid formation while being urged by said resilient element against saidstop means, said extension engaging said stop means substantially in amidposition of a pendulum swing. .Iaddend. .Iadd.22. In a timepiece, incombination: a clockwork powered by a source of electric energy; atorsion pendulum with an elongate resilient element having a fixedlyanchored upper end and a freely rotatable weighted lower end, saidresilient element being provided with a transverse spur secured theretonear said upper end for oscillation thereabout; mechanical transmissionmeans forming a power train between said clockwork and said resilientelement for periodically stepping said torsion pendulum, saidtransmission means including a driving member positively coupled withsaid clockwork, a driven member having a formation intermittentlyengageable with said spur during a predetermined phase of eachoscillatory cycle of said torsion pendulum, and a releasable couplingbetween said driving and driven members yieldable to interrupt saidpower train upon said driven member encountering a significantresistance; and stop means in the path of said spur for arresting sameduring a predetermined fraction of each oscillatory cycle while allowingsaid torsion pendulum to complete the cycle at an accelerated rateresulting from a partial immobilization of said resilient element, saidformation coacting with said spur during said fraction whereby saiddriven member encounters a resistance sufficient to release saidcoupling until said spur disengages said stop means following a reversalof the rotation of said torsion pendulum. .Iaddend. .Iadd.23. Thecombination defined in claim 22 wherein said stop means is positionedfor engagement by said spur substantially in a midposition of anoscillatory swing of said lower end. .Iaddend. .Iadd.24. The combinationdefined in claim 23 wherein said driven member is a cam disk with asubstantially horizontal axis, said formation being at least one hump onsaid cam disk, said stop means substantially coinciding with a verticalplane including said axis. .Iaddend. .Iadd.25. The combination definedin claim 22 wherein said clockwork comprises an electrodynamicescapement. .Iaddend.